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System

Job No.

Function of fuel tank with splash pot 47 Function of fuel gauge sending unit 47 020Function of fuel gauge sending unit Turbodiesel 47 020Function of fuel tank breather and vent 47 030Function of fuel tank ventilation Turbodiesel 47 030Removal and installation of fuel tank 47 Removal and installation of fuel gauge sending unit 47 120

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Function of fuel tank with splash pot

Model 201 naturally-asprrated

67 Splash pot

68 Fuel

70 Return

Return nozzle

The sheet steel fuel tank is fitted with a splashpot (67). The purpose of this is to ensure that

the engine is reliably supplied with fuel when the

fuel level in the tank is low and when negotiating

a lengthy series of curves.

When the fuel pump is running, the return fuel

jet flows at a high speed out of the return nozzle

(7011) into the splash pot. In this way it draws

fuel around the return nozzle into the splash pot

as well.

The level of fuel (h) in the splash pot is main-

tained even if the fuel level in the tank drops

below the height (h).

47 10 I I I - 0 10 1

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Model 2 01 , 1 2 4, 1 26 Turbocharged engines

67 Splash pot 70

68 Fuel 7011

Return

Return nozzle

47 10

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Function of fuel gauge sending unit

1 contact

2 Float

3 Contact plate

4 and contact rod

5 Re s e r v e contact

As the fuel level drops, the resistance is

increased by the wiper contact ( 1 ) . At the float

the voltage drops and the gauge needle in

the instrument cluster moves back.

If the fuel level drops to the reserve quantity, the

reserve warning contact (5) closes and switches

ground to the reserve warning lamp. The reserve

warning lamp lights up when the ignition

is switched on (check function).

As soon as the engine starts, the lamp goes out

provided there is more fuel in the tank than the

reserve quantity.

4 7 1 0 I I I

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Note

The reserve warning lamp shows a weaker light

for the check function, and a stronger light to

indicate reserve quantity.

Check fuel gauge (54-269).

Fuel gauge sending unit, Model 201

The installation angle has been modified from

approx. (off perpendicular) to approx.

The instrument gauge has been adapted to thenew sending unit position (refer to Group 5 4 ) .

Repair instructions

The modified sending unit may also be fitted

in place of the existing sending unit but

not vice versa.

Standard implementation: July 1987

Vehicle No.

A 394 178

F 390 243

Modifications effective (Model Care)

The fuel gauge sending unit has been modified

at the flange and in its length such that it is valid

for all fuel tanks of Model 201 effective

4 7. 1 0 I I I

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Function of fuel gauge Sending unit Turbodiesel

5 - - -

1 contact

2 Float

3 Contact plate

4 and contact rod

5 Reserve fuel

If the fuel level drops, the resistance is increased

by the wiper contact (1) on the float the

voltage drops and the needle on the gauge in

the instrument cluster moves back.

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If the fuel level drops to reserve quantity, the

reserve warning contact (5) closes and switches

ground to the reserve warning lamp. The reserve

warning lamp lights up if the ignition is switched

on (indicating function). As soon as the engine is

running, it goes out provided there is more fuel

in the tank than the reserve quantity.

Note

The reserve fuel warning lamp shows a weaker

light for the indicating function and a stronger

light for the reserve quantity.

Check fuel gauge (54-257).

4 7. 1 0

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47-030 Function of fuel tank breather and vent

Filler cap

0 0 4 1 - 5 3

All models

1 cap2 ring

3 Locking bar

4 spring

5 neck

The fuel evaporation gases escape through the

filler cap at a pressure of 100-300 mbar gauge.

This only occurs, if, for example, the passage

in the vent line from the fuel tank is not clear. If

the system is operating properly, anoverpressure of up to 50 mbar may be present

in the fuel tank.

47 10 I I I

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51

5 0 Fuel tank

51 Vent valve

rubber boot

54 Central

breaker

64 Vent

The vent system consists of a central pipe (54)

with an siphon breaker at each end.

The siphon breakers prevent fuel escaping

along the vent line. The vent line (64) runs from

the central pipe to the vent valve (51).

If an overpressure of 30-50 mbar is reached in

the fuel tank, the vent valve (4) opens and the

fuel vapors flow to the charcoal canister.

1 Compression

2 Valve housing

3 plate

4 Vent valve5 Valve plate

6 valve

7 Connection fitting

47.10 III

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If a vacuum of l - l 6 mbar is produced in the fuel

tank, the air admission valve (6) opens.

The protective rubber boot at the end of the vent

valve prevents dirt and splash water entering the

vent valve.

Standard implementation:

Model

201

Vehicle No.

April 1986 May 1986

A 296211 F 227064

Vent system modified

The vent system has been modified by the

addition of lines and siphon breakers (arrows) so

that no fuel can escape through the vent system

even under extreme conditions (rollover).

Standard implementation: phased-in (approx.

1

- 0 0 6 6 - 1 5

4 7. 1 0 I I I

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Function of fuel tank ventilation

All Turbodiesel models

1

2

3 bar

At a gauge pressure of 100-300 mbar, vaporized

fuel can escape through the fuel cap. This is

only the case if the vent line from the fuel tank is

not clear. If the system is operating properly, a

gauge pressure of up to 50 mbar may be

present in the fuel tank.

Compression spring

neck

1 0 I I I

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5 4 6 4

The vent system the fuel tank (50) consists of

a central pipe ( 5 4 ) each with a siphon breaker

( 5 4 1) at the ends. The siphon breakers prevent

fuel escaping through the vent line.

The vent (64) runs from the central pipe to

the vent valve (51). The protective seal at

the end of the vent valve prevents dirt and

splash water from getting into the vent valve.

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If a gauge pressure of 30-50 mbar is present in

the fuel tank, the vent valve (4) opens and

allows the fuel vapors to escape.

1 Compression

2 Valve

3 plate

4 Vent valve

5 Valve plate6 valve

7

If a vacuum of 1-16 mbar is produced in the fuel

tank, the air admission valve (6) opens.

Station wagons

These models are fitted with a modified vent

valve with a bright base section. The

performance is the same as for other vent

valves.

1 Compression spring

2 Valve housing

3 Spring plate

4 Vent valve

5 Valve plate

6 valve7 Connection

The dirt seal at the end of the vent valve

prevents dirt and splash water from getting into

the vent valve.

4 7. 1 0 III 03013

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Modified vent system

The vent system has been modified by additional

lines and siphon breakers (arrows) with the

result that no fuel can escape through the vent

system, even under extreme conditions

(rollover).

Production breakpoint: phased in (approx.

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Model 201 naturally-aspirated versions

6 2

Safety regulations Observe, risk of accident!

Battery ground cable Disconnect, connect.

Filler cap (62) Remove, fit. Check seal replace if

Fuel tank (50)

Cup seal . . . . . . . . . . . . . . . . . . Remove, Install.

Lining of fuel tank . . . . . Detach, attach.

necessary.

. . . . . . . . . . . . . . . . . . Drain. Carefully pump out fuel to ensure no

fuel remains in the tank. Capacity approx.

55 liters ( 1 4. 5 US gal.)

Stick on 4 sound-absorbing strips if

necessary, with MB Universal Adhesive

000 989 92 71 (steel fuel tank only).

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Model 201 versions

62

65

Safety regulations

Battery ground cable

Cap(62) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fuel tank (50)

observe, risk of accident!

disconnect, connect.

remove, install. Check seal renew if

necessary.

drain. Carefully pump out fuel to ensure that

there is no fuel remaining in the tank. Capacity

approx. 55 litres. Stick 4 sound-deadening strips

(74) with MB adhesive 000 989 92 7 1,

if necessary.

4 7. 1 0 I I I 10019

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